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Abstract:

Methods are disclosed for controlling the rate of cellulose hydrolysis
and reducing the rate of glucose degradation by adjusting the pH during
cellulose hydrolysis.

Claims:

1. A method of controlling the rate of cellulose hydrolysis, comprising:
providing lignocellulosic biomass at a first pressure greater than
atmospheric pressure, comprising: a first solid fraction comprising:
cellulose; and lignin; and a first liquid fraction; separating said first
solid fraction from said first liquid fraction; mixing said first solid
fraction with water to form a slurry; wherein said slurry has a pH of
about pH 3.0 to about pH 4.5; increasing said pH of said slurry by about
0.5 pH units to about 5.0 pH units to form an adjusted pH slurry;
optionally, pre-heating said adjusted pH slurry to a temperature less
than the critical point of water; contacting said adjusted pH slurry with
a second reaction fluid comprising supercritical or near-supercritical
fluid to form a reaction mixture comprising: a second solid fraction
comprising: lignin; and a second liquid fraction comprising: a soluble
C6 saccharide selected from the group consisting of
cello-oligosaccharides, glucose, galactose, mannose, fructose, and
mixtures thereof; wherein said supercritical or near-critical fluid
comprises water and, optionally, CO2; and wherein said contacting
said adjusted pH slurry with said second reaction fluid has a duration
greater than about 2 seconds; optionally, reducing the temperature of
said reaction mixture to a temperature below about 280.degree. C.; and
optionally, hydrolyzing said second liquid fraction to form a C6
saccharide selected from the group consisting of C6 oligosaccharide
having lower mer units, glucose, galactose, mannose, fructose, and
mixtures thereof.

2. A method of claim 1, wherein said method is continuous.

3. A method of claim 1, wherein said supercritical or near-critical fluid
is substantially free of C1-C5 alcohols.

4. A method of claim 1, wherein said step of contacting said adjusted pH
slurry with said second reaction fluid is carried out substantially free
of catalyst other than carbon dioxide.

5. A method of claim 4, wherein said catalyst is an acid.

6. A method of claim 1, further comprising: fractionating said
lignocellulosic biomass prior to said providing step; wherein said step
of fractionating comprises contacting said lignocellulosic biomass with a
first reaction fluid comprising hot compressed water and, optionally,
carbon dioxide; wherein said first reaction fluid further comprises acid,
when said lignocellulosic biomass comprises softwood; and wherein said
first reaction fluid is at a temperature of at least about 100.degree. C.
under a pressure sufficient to maintain said first reaction fluid in
liquid form.

7. A method of claim 1, wherein said step of contacting said adjusted pH
slurry with said second reaction fluid has a duration greater than about
2 seconds to about 5 seconds.

8. A method of claim 1, wherein said step of contacting said adjusted pH
slurry with said second reaction fluid has a duration about 5 seconds to
about 10 seconds.

9. A method of claim 1, wherein said adjusted pH slurry has a pH of about
pH 5.0 to about pH 8.0.

10. A method of claim 1, wherein said adjusted pH slurry has a pH of
about pH 5.0 to about pH 6.0.

11. A method of claim 1, wherein said step of increasing said pH of said
slurry comprises adding a base; wherein said base is selected from the
group consisting of an organic base, an inorganic base, and combinations
thereof.

12. A method of claim 11, wherein said inorganic base is a compound
selected from the group consisting of sodium hydroxide, ammonium
hydroxide, calcium carbonate, and combinations thereof.

13. A method of claim 12, wherein said inorganic base is sodium
hydroxide.

14. A method of claim 1, wherein the yield of said glucose is at least
60% of theoretical yield.

15. A product produced by the method of claim 1.

16. A method of reducing the rate of glucose degradation, comprising:
providing lignocellulosic biomass at a first pressure greater than
atmospheric pressure, comprising: a first solid fraction comprising:
cellulose; and lignin; and a first liquid fraction; separating said first
solid fraction from said first liquid fraction; mixing said first solid
fraction with water to form a slurry; wherein said slurry has a pH of
about pH 3.0 to about pH 4.5; increasing said pH of said slurry by about
0.5 pH units to about 5.0 pH units to form an adjusted pH slurry;
optionally, pre-heating said adjusted pH slurry to a temperature less
than the critical point of water; contacting said adjusted pH slurry with
a second reaction fluid comprising supercritical or near-supercritical
fluid to form a reaction mixture comprising: a second solid fraction
comprising: lignin; and a second liquid fraction comprising: a soluble
C6 saccharide selected from the group consisting of
cello-oligosaccharides, glucose, galactose, mannose, fructose, and
mixtures thereof; wherein said supercritical or near-critical fluid
comprises water and, optionally, CO2; and wherein said contacting
said adjusted pH slurry with a second reaction fluid has a duration
greater than about 2 seconds; optionally, reducing the temperature of
said reaction mixture to a temperature below about 280.degree. C.; and
optionally, hydrolyzing said second liquid fraction to form a C6
saccharide selected from the group consisting of C6 oligosaccharide
having lower mer units, glucose, galactose, mannose, fructose, and
mixtures thereof.

17. A method of claim 16, wherein said method is continuous.

18. A method of claim 16, wherein said supercritical or near-critical
fluid is substantially free of C1-C5 alcohols.

19. A method of claim 16, wherein said step of contacting said adjusted
pH slurry with said second reaction fluid is carried out substantially
free of catalyst other than carbon dioxide.

20. A method of claim 19, wherein said catalyst is an acid.

21. A method of claim 16, further comprising: fractionating said
lignocellulosic biomass prior to said providing step; wherein said step
of fractionating comprises contacting said lignocellulosic biomass with a
first reaction fluid comprising hot compressed water and, optionally,
carbon dioxide; wherein said first reaction fluid further comprises acid,
when said lignocellulosic biomass comprises softwood; and wherein said
first reaction fluid is at a temperature of at least about 100.degree. C.
under a pressure sufficient to maintain said first reaction fluid in
liquid form.

22. A method of claim 16, wherein said step of contacting said adjusted
pH slurry with said second reaction fluid has a duration greater than
about 2 seconds to about 5 seconds.

23. A method of claim 16, wherein said step of contacting said adjusted
pH slurry with said second reaction fluid has a duration about 5 seconds
to about 10 seconds.

24. A method of claim 16, wherein said adjusted pH slurry has a pH of
about pH 5.0 to about pH 8.0.

25. A method of claim 16, wherein said adjusted pH slurry has a pH of
about pH 5.0 to about pH 6.0.

26. A method of claim 16, wherein said step of increasing said pH of said
slurry comprises adding a base; wherein said base is selected from the
group consisting of an organic base, an inorganic base, and combinations
thereof.

27. A method of claim 26, wherein said inorganic base is a compound
selected from the group consisting of sodium hydroxide, ammonium
hydroxide, calcium carbonate, and combinations thereof.

28. A method of claim 27, wherein said inorganic base is sodium
hydroxide.

29. A method of claim 16, wherein the yield of said glucose is at least
60% of theoretical yield.

30. A product produced by the method of claim 16.

31. A composition formed from lignocellulosic biomass, comprising:
C6 saccharide; less than about 15%, by weight, based on the total
weight of the composition, of byproducts, wherein said byproducts are
selected from the group consisting of glycolaldehyde, glycolic acid,
glyceraldehyde, and mixtures thereof; and water; wherein said C6
saccharides are produced from said lignocellulosic biomass using
supercritical or near critical fluids.

32. A composition of claim 31, wherein said C6 saccharide is
glucose, galactose, mannose, fructose, or a mixture thereof.

33. A composition of claim 31, wherein said C6 saccharide is
glucose.

34. A method, comprising: providing lignocellulosic biomass at a first
pressure greater than atmospheric pressure, comprising: a first solid
fraction comprising: cellulose; and lignin; and a first liquid fraction;
separating said first solid fraction from said first liquid fraction;
mixing said first solid fraction with water to form a slurry; wherein
said slurry has a pH of about pH 3.0 to about pH 4.5; increasing said pH
of said slurry by about 0.5 pH units to about 5.0 pH units to form an
adjusted pH slurry; optionally, pre-heating said adjusted pH slurry to a
temperature less than the critical point of water; contacting said
adjusted pH slurry with a second reaction fluid comprising supercritical
or near-supercritical fluid to form a reaction mixture comprising: a
second solid fraction comprising: lignin; and a second liquid fraction
comprising: a soluble C6 saccharide selected from the group
consisting of cello-oligosaccharides, glucose, galactose, mannose,
fructose, and mixtures thereof; wherein said supercritical or
near-critical fluid comprises water and, optionally, CO2; and
wherein said contacting said adjusted pH slurry with a second reaction
fluid has a duration greater than about 2 seconds; reducing the
temperature of said reaction mixture to a temperature below about
280.degree. C.; hydrolyzing said second liquid fraction to form C6
saccharides selected from the group consisting of C6 oligosaccharide
having lower mer units, glucose, galactose, mannose, fructose, and
mixtures thereof; and converting by fermentation, catalysis, or a
combination thereof said C6 saccharides to a fermentation product, a
catalysis product, or a mixture thereof.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The application claims the benefit of U.S. Application No.
61/482,465, filed May 4, 2011, the entire disclosure of which is
incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention generally relates to methods for controlling
the rate of cellulose hydrolysis and reducing the rate of glucose
degradation. More particularly, it relates to methods for controlling the
rate of cellulose hydrolysis and reducing the rate of glucose degradation
by adjusting the pH during cellulose hydrolysis.

BACKGROUND OF THE INVENTION

[0003] There exist methods for converting lignocellulosic biomass into
fermentable C5 and C6 sugars. Several of these methods first
produce oligomers of the C5 and C6 sugars, which are then
hydrolyzed to form fermentable streams of monomers of C5 and C6
sugars. Problems exist with current methods, including, inter alia, that
due to the very short residence times in the reactor there are control
issues often lead to unwanted degradation products, such as acids that
inhibit fermentation. It would, therefore, be beneficial to develop
methods that would be scalable and controllable, that maximize monomer
formation, and that minimize the formation of degradation products. The
methods and compositions of the present invention are directed toward
these, as well as other, important ends.

SUMMARY OF THE INVENTION

[0004] In one embodiment, the invention is directed to methods of
increasing the level of C6 monosaccharides produced from
lignocellulosic biomass, comprising: [0005] providing lignocellulosic
biomass at a first pressure greater than atmospheric pressure,
comprising: [0006] a first solid fraction comprising: [0007] cellulose;
and [0008] lignin; and [0009] a first liquid fraction; [0010]
separating said first solid fraction from said first liquid fraction;
[0011] mixing said first solid fraction with water to form a slurry;
[0012] wherein said slurry has a pH of about pH 3.0 to about pH 4.5;
[0013] increasing said pH of said slurry by about 0.5 pH units to about
5.0 pH units to form an adjusted pH slurry; [0014] optionally,
pre-heating said adjusted pH slurry to a temperature less than the
critical point of water; [0015] contacting said adjusted pH slurry with a
second reaction fluid comprising supercritical or near-supercritical
fluid to form a reaction mixture comprising: [0016] a second solid
fraction comprising: [0017] lignin; and [0018] a second liquid
fraction comprising: [0019] a soluble C6 saccharide selected from
the group consisting of cello-oligosaccharides, glucose, galactose,
mannose, fructose, and mixtures thereof; [0020] wherein said
supercritical or near-critical fluid comprises water and, optionally,
CO2; and [0021] wherein said contacting said adjusted pH slurry with
a second reaction fluid has a duration greater than about 2 seconds;
[0022] optionally, reducing the temperature of said reaction mixture to a
temperature below about 280° C.; and [0023] optionally,
hydrolyzing said second liquid fraction to form a C6 saccharide
selected from the group consisting of C6 oligosaccharide having
lower mer units, glucose, galactose, mannose, fructose, and mixtures
thereof.

[0024] In another embodiment, the invention is directed to methods of
controlling the rate of cellulose hydrolysis, comprising: [0025]
providing lignocellulosic biomass at a first pressure greater than
atmospheric pressure, comprising: [0026] a first solid fraction
comprising: [0027] cellulose; and [0028] lignin; and [0029] a first
liquid fraction; [0030] separating said first solid fraction from said
first liquid fraction; [0031] mixing said first solid fraction with water
to form a slurry; [0032] wherein said slurry has a pH of about pH 3.0 to
about pH 4.5; [0033] increasing said pH of said slurry by about 0.5 pH
units to about 5.0 pH units to form an adjusted pH slurry; [0034]
optionally, pre-heating said adjusted pH slurry to a temperature less
than the critical point of water; [0035] contacting said adjusted pH
slurry with a second reaction fluid comprising supercritical or
near-supercritical fluid to form a reaction mixture comprising: [0036] a
second solid fraction comprising: [0037] lignin; and [0038] a second
liquid fraction comprising: [0039] a soluble C6 saccharide selected
from the group consisting of cello-oligosaccharides, glucose, galactose,
mannose, fructose, and mixtures thereof; [0040] wherein said
supercritical or near-critical fluid comprises water and, optionally,
CO2; and [0041] wherein said contacting said adjusted pH slurry with
a second reaction fluid has a duration greater than about 2 seconds;
[0042] optionally, reducing the temperature of said reaction mixture to a
temperature below about 280° C.; and [0043] optionally,
hydrolyzing said second liquid fraction to form a C6 saccharide
selected from the group consisting of C6 oligosaccharide having
lower mer units, glucose, galactose, mannose, fructose, and mixtures
thereof.

[0044] In yet other embodiments, the invention is directed to methods of
reducing the rate of glucose degradation, comprising: [0045] providing
lignocellulosic biomass at a first pressure greater than atmospheric
pressure, comprising: [0046] a first solid fraction comprising: [0047]
cellulose; and [0048] lignin; and [0049] a first liquid fraction;
[0050] separating said first solid fraction from said first liquid
fraction; [0051] mixing said first solid fraction with water to form a
slurry; [0052] wherein said slurry has a pH of about pH 3.0 to about pH
4.5; [0053] increasing said pH of said slurry by about 0.5 pH units to
about 5.0 pH units to form an adjusted pH slurry; [0054] optionally,
pre-heating said adjusted pH slurry to a temperature less than the
critical point of water; [0055] contacting said adjusted pH slurry with a
second reaction fluid comprising supercritical or near-supercritical
fluid to form a reaction mixture comprising: [0056] a second solid
fraction comprising: [0057] lignin; and [0058] a second liquid
fraction comprising: [0059] a soluble C6 saccharide selected from
the group consisting of cello-oligosaccharides, glucose, galactose,
mannose, fructose, and mixtures thereof; [0060] wherein said
supercritical or near-critical fluid comprises water and, optionally,
CO2; and [0061] wherein said contacting said adjusted pH slurry with
a second reaction fluid has a duration greater than about 2 seconds;
[0062] optionally, reducing the temperature of said reaction mixture to a
temperature below about 280° C.; and [0063] optionally,
hydrolyzing said second liquid fraction to form a C6 saccharide
selected from the group consisting of C6 oligosaccharide having
lower mer units, glucose, galactose, mannose, fructose, and mixtures
thereof.

[0064] In other embodiments, the invention is directed to methods,
comprising: [0065] providing lignocellulosic biomass at a first
pressure greater than atmospheric pressure, comprising: [0066] a first
solid fraction comprising: [0067] cellulose; and [0068] lignin; and
[0069] a first liquid fraction; [0070] separating said first solid
fraction from said first liquid fraction; [0071] mixing said first solid
fraction with water to form a slurry; [0072] wherein said slurry has a pH
of about pH 3.0 to about pH 4.5; [0073] increasing said pH of said slurry
by about 0.5 pH units to about 5.0 pH units to form an adjusted pH
slurry; [0074] optionally, pre-heating said adjusted pH slurry to a
temperature less than the critical point of water; [0075] contacting said
adjusted pH slurry with a second reaction fluid comprising supercritical
or near-supercritical fluid to form a reaction mixture comprising:
[0076] a second solid fraction comprising: [0077] lignin; and [0078] a
second liquid fraction comprising: [0079] a soluble C6 saccharide
selected from the group consisting of cello-oligosaccharides, glucose,
galactose, mannose, fructose, and mixtures thereof; [0080] wherein said
supercritical or near-critical fluid comprises water and, optionally,
CO2; and [0081] wherein said contacting said adjusted pH slurry with
a second reaction fluid has a duration greater than about 2 seconds;
[0082] reducing the temperature of said reaction mixture to a temperature
below about 280° C.; [0083] hydrolyzing said second liquid
fraction to form C6 saccharides selected from the group consisting
of C6 oligosaccharide having lower mer units, glucose, galactose,
mannose, fructose, and mixtures thereof; and [0084] converting by
fermentation, catalysis, or a combination thereof said C6
saccharides to a fermentation product, a catalysis product, or a mixture
thereof.

[0085] In further embodiments, the invention is directed to compositions
formed from lignocellulosic biomass, comprising:

[0086] C6 saccharide;

[0087] less than about 15%, preferably, less than about 10%, by weight,
based on the total weight of the composition, of byproducts, wherein said
byproducts are selected from the group consisting of glycolaldehyde,
glycolic acid, glyceraldehyde, and mixtures thereof; and

[0088] water;

[0089] wherein said C6 saccharides are produced from said
lignocellulosic biomass using supercritical or near critical fluids.

BRIEF DESCRIPTION OF THE DRAWINGS

[0090] The accompanying drawings, which are included to provide a further
understanding of the invention and are incorporated in and constitute a
part of this specification, illustrate embodiments of the invention and
together with the description serve to explain the principles of the
invention. In the drawings:

[0091] FIG. 1 is a plot of % cellulose conversion as a function of pH at
different residence times at a temperature of 335° C. for one
embodiment of the invention.

[0092]FIG. 2 is a plot of % glucose yield as a function of pH at
different residence time of 335° C.

[0093] FIG. 3 is a plot of % cellulose conversion as a function of
temperature at different pH for a 5 s residence time for one embodiment
of the invention.

[0094]FIG. 4 is a plot of % cellulose conversion as a function of
temperature at different pH for a 7 s residence time for one embodiment
of the invention.

[0095]FIG. 5 is a plot of % glucose yield as a function of temperature at
different pH for a 7 s residence time for one embodiment of the
invention.

[0096]FIG. 6 is a plot of % C6 saccharide yield as a function pH at
375° C. for different residence times for one embodiment of the
invention.

[0097] FIG. 7 is a plot of % cellulose conversion as a function of pH at
375° C. for different residence times for one embodiment of the
invention.

DETAILED DESCRIPTION OF THE INVENTION

[0098] As employed above and throughout the disclosure, the following
terms, unless otherwise indicated, shall be understood to have the
following meanings.

[0099] As used herein, the singular forms "a," "an," and "the" include the
plural reference unless the context clearly indicates otherwise.

[0100] While the present invention is capable of being embodied in various
forms, the description below of several embodiments is made with the
understanding that the present disclosure is to be considered as an
exemplification of the invention, and is not intended to limit the
invention to the specific embodiments illustrated. Headings are provided
for convenience only and are not to be construed to limit the invention
in any manner. Embodiments illustrated under any heading may be combined
with embodiments illustrated under any other heading.

[0101] The use of numerical values in the various quantitative values
specified in this application, unless expressly indicated otherwise, are
stated as approximations as though the minimum and maximum values within
the stated ranges were both preceded by the word "about." In this manner,
slight variations from a stated value can be used to achieve
substantially the same results as the stated value. Also, the disclosure
of ranges is intended as a continuous range including every value between
the minimum and maximum values recited as well as any ranges that can be
formed by such values. Also disclosed herein are any and all ratios (and
ranges of any such ratios) that can be formed by dividing a recited
numeric value into any other recited numeric value. Accordingly, the
skilled person will appreciate that many such ratios, ranges, and ranges
of ratios can be unambiguously derived from the numerical values
presented herein and in all instances such ratios, ranges, and ranges of
ratios represent various embodiments of the present invention.

[0102] As used herein, the phrase "substantially free" means have no more
than about 1%, preferably less than about 0.5%, more preferably, less
than about 0.1%, by weight of a component, based on the total weight of
any composition containing the component.

[0103] A supercritical fluid is a fluid at a temperature above its
critical temperature and at a pressure above its critical pressure. A
supercritical fluid exists at or above its "critical point," the point of
highest temperature and pressure at which the liquid and vapor (gas)
phases can exist in equilibrium with one another. Above critical pressure
and critical temperature, the distinction between liquid and gas phases
disappears. A supercritical fluid possesses approximately the penetration
properties of a gas simultaneously with the solvent properties of a
liquid. Accordingly, supercritical fluid extraction has the benefit of
high penetrability and good solvation.

[0104] Reported critical temperatures and pressures include: for pure
water, a critical temperature of about 374.2° C., and a critical
pressure of about 221 bar; for carbon dioxide, a critical temperature of
about 31° C. and a critical pressure of about 72.9 atmospheres
(about 1072 psig). Near-critical water has a temperature at or above
about 300° C. and below the critical temperature of water
(374.2° C.), and a pressure high enough to ensure that all fluid
is in the liquid phase. Sub-critical water has a temperature of less than
about 300° C. and a pressure high enough to ensure that all fluid
is in the liquid phase. Sub-critical water temperature may be greater
than about 250° C. and less than about 300° C., and in many
instances sub-critical water has a temperature between about 250°
C. and about 280° C. The term "hot compressed water" is used
interchangeably herein for water that is at or above its critical state,
or defined herein as near-critical or sub-critical, or any other
temperature above about 50° C. (preferably, at least about
100° C.) but less than subcritical and at pressures such that
water is in a liquid state

[0105] As used herein, a fluid which is "supercritical" (e.g.
supercritical water, supercritical CO2, etc.) indicates a fluid
which would be supercritical if present in pure form under a given set of
temperature and pressure conditions. For example, "supercritical water"
indicates water present at a temperature of at least about 374.2°
C. and a pressure of at least about 221 bar, whether the water is pure
water, or present as a mixture (e.g. water and ethanol, water and
CO2, etc.). Thus, for example, "a mixture of sub-critical water and
supercritical carbon dioxide" indicates a mixture of water and carbon
dioxide at a temperature and pressure above that of the critical point
for carbon dioxide but below the critical point for water, regardless of
whether the supercritical phase contains water and regardless of whether
the water phase contains any carbon dioxide. For example, a mixture of
sub-critical water and supercritical CO2 may have a temperature of
about 250° C. to about 280° C. and a pressure of at least
about 225 bar.

[0106] As used herein, "continuous" indicates a process which is
uninterrupted for its duration, or interrupted, paused or suspended only
momentarily relative to the duration of the process. Treatment of biomass
is "continuous" when biomass is fed into the apparatus without
interruption or without a substantial interruption, or processing of said
biomass is not done in a batch process.

[0107] As used herein, "resides" indicates the length of time which a
given portion or bolus of material is within a reaction zone or reactor
vessel. The "residence time," as used herein, including the examples and
data, are reported at ambient conditions and are not necessarily actual
time elapsed.

[0108] As used herein, the term "substantial free of" refers to a
composition having less than about 1% by weight, preferably less than
about 0.5% by weight, and more preferably less than about 0.1% by weight,
based on the total weight of the composition, of the stated material.

[0109] As used herein, "C1-C5 alcohol" indicates an alcohol
comprising 1 to 5 carbon atoms. Examples of C1-C5 alcohols
include, but are not limited to, methanol, ethanol, n-propanol,
isopropanol, n-butanol, s-butanol, t-butanol, i-butanol, n-pentanol,
2-pentanol, 3-pentanol, 2-methyl-1-butanol, 2-methyl-2-butanol,
3-methyl-1-butanol, 3-methyl-2-butanol, and 2,2-dimethyl-1-propanol.
Mixtures of one or more of these alcohols may be used.

[0111] Accordingly, in one embodiment, the invention is directed to
methods of increasing the level of C6 monosaccharides produced from
lignocellulosic biomass, comprising: [0112] providing lignocellulosic
biomass at a first pressure greater than atmospheric pressure,
comprising: [0113] a first solid fraction comprising: [0114] cellulose;
and [0115] lignin; and [0116] a first liquid fraction; [0117]
separating said first solid fraction from said first liquid fraction;
[0118] mixing said first solid fraction with water to form a slurry;
[0119] wherein said slurry has a pH of about pH 3.0 to about pH 4.5;
[0120] increasing said pH of said slurry by about 0.5 pH units to about
5.0 pH units to form an adjusted pH slurry; [0121] optionally,
pre-heating said adjusted pH slurry to a temperature less than critical
point of water; [0122] contacting said adjusted pH slurry with a second
reaction fluid comprising supercritical or near-supercritical fluid to
form a reaction mixture comprising: [0123] a second solid fraction
comprising: [0124] lignin; and [0125] a second liquid fraction
comprising: [0126] a soluble C6 saccharide selected from the group
consisting of cello-oligosaccharides, glucose, galactose, mannose,
fructose, and mixtures thereof; [0127] wherein said supercritical or
near-critical fluid comprises water and, optionally, CO2; and
[0128] wherein said contacting said adjusted pH slurry with a second
reaction fluid has a duration greater than about 2 seconds; [0129]
optionally, reducing the temperature of said reaction mixture to a
temperature below about 280° C.; and [0130] optionally,
hydrolyzing said second liquid fraction to form a C6 saccharide
selected from the group consisting of C6 oligosaccharide having
lower mer units (relative to the oligosaccharides in said second liquid
fraction), glucose, galactose, mannose, fructose, and mixtures thereof.

[0131] In another embodiment, the invention is directed to methods of
controlling the rate of cellulose hydrolysis, comprising: [0132]
providing lignocellulosic biomass at a first pressure greater than
atmospheric pressure, comprising: [0133] a first solid fraction
comprising: [0134] cellulose; and [0135] lignin; and [0136] a first
liquid fraction; [0137] separating said first solid fraction from said
first liquid fraction; [0138] mixing said first solid fraction with water
to form a slurry; [0139] wherein said slurry has a pH of about pH 3.0 to
about pH 4.5; [0140] increasing said pH of said slurry by about 0.5 pH
units to about 5.0 pH units to form an adjusted pH slurry; [0141]
optionally, pre-heating said adjusted pH slurry to a temperature less
than critical point of water; [0142] contacting said adjusted pH slurry
with a second reaction fluid comprising supercritical or
near-supercritical fluid to form a reaction mixture comprising: [0143] a
second solid fraction comprising: [0144] lignin; and [0145] a second
liquid fraction comprising: [0146] a soluble C6 saccharide selected
from the group consisting of cello-oligosaccharides, glucose, galactose,
mannose, fructose, and mixtures thereof; [0147] wherein said
supercritical or near-critical fluid comprises water and, optionally,
CO2; and [0148] wherein said contacting said adjusted pH slurry with
a second reaction fluid has a duration greater than about 2 seconds;
[0149] optionally, reducing the temperature of said reaction mixture to a
temperature below about 280° C.; and [0150] optionally,
hydrolyzing said second liquid fraction to form a C6 saccharide
selected from the group consisting of C6 oligosaccharide having
lower mer units (relative to the oligosaccharides in said second liquid
fraction), glucose, galactose, mannose, fructose, and mixtures thereof.

[0151] In yet other embodiments, the invention is directed to methods of
reducing the rate of glucose degradation, comprising: [0152] providing
lignocellulosic biomass at a first pressure greater than atmospheric
pressure, comprising: [0153] a first solid fraction comprising: [0154]
cellulose; and [0155] lignin; and [0156] a first liquid fraction;
[0157] separating said first solid fraction from said first liquid
fraction; [0158] mixing said first solid fraction with water to form a
slurry; [0159] wherein said slurry has a pH of about pH 3.0 to about pH
4.5; [0160] increasing said pH of said slurry by about 0.5 pH units to
about 5.0 pH units to form an adjusted pH slurry; [0161] optionally,
pre-heating said adjusted pH slurry to a temperature less than critical
point of water; [0162] contacting said adjusted pH slurry with a second
reaction fluid comprising supercritical or near-supercritical fluid to
form a reaction mixture comprising: [0163] a second solid fraction
comprising: [0164] lignin; and [0165] a second liquid fraction
comprising: [0166] a soluble C6 saccharide selected from the group
consisting of cello-oligosaccharides, glucose, galactose, mannose,
fructose, and mixtures thereof; [0167] wherein said supercritical or
near-critical fluid comprises water and, optionally, CO2; and [0168]
wherein said contacting said adjusted pH slurry with a second reaction
fluid has a duration greater than about 2 seconds; [0169] optionally,
reducing the temperature of said reaction mixture to a temperature below
about 280° C.; and [0170] optionally, hydrolyzing said second
liquid fraction to form a C6 saccharide selected from the group
consisting of C6 oligosaccharide having lower mer units (relative to
the oligosaccharides in said second liquid fraction), glucose, galactose,
mannose, fructose, and mixtures thereof.

[0171] In other embodiments, the invention is directed to methods,
comprising: [0172] providing lignocellulosic biomass at a first
pressure greater than atmospheric pressure, comprising: [0173] a first
solid fraction comprising: [0174] cellulose; and [0175] lignin; and
[0176] a first liquid fraction; [0177] separating said first solid
fraction from said first liquid fraction; [0178] mixing said first solid
fraction with water to form a slurry; [0179] wherein said slurry has a pH
of about pH 3.0 to about pH 4.5; [0180] increasing said pH of said slurry
by about 0.5 pH units to about 5.0 pH units to form an adjusted pH
slurry; [0181] optionally, pre-heating said adjusted pH slurry to a
temperature less than critical point of water; [0182] contacting said
adjusted pH slurry with a second reaction fluid comprising supercritical
or near-supercritical fluid to form a reaction mixture comprising:
[0183] a second solid fraction comprising: [0184] lignin; and [0185] a
second liquid fraction comprising: [0186] a soluble C6 saccharide
selected from the group consisting of cello-oligosaccharides, glucose,
galactose, mannose, fructose, and mixtures thereof; [0187] wherein said
supercritical or near-critical fluid comprises water and, optionally,
CO2; and [0188] wherein said contacting said adjusted pH slurry with
a second reaction fluid has a duration greater than about 2 seconds;
[0189] reducing the temperature of said reaction mixture to a temperature
below about 280° C.; [0190] hydrolyzing said second liquid
fraction to form C6 saccharides selected from the group consisting
of C6 oligosaccharide having lower mer units, glucose, galactose,
mannose, fructose, and mixtures thereof; and [0191] converting by
fermentation, catalysis, or a combination thereof said C6
saccharides to a fermentation product, a catalysis product, or a mixture
thereof. Such products include, for example, ethanol and butanol, and
mixtures thereof.

[0192] In certain embodiments of the method, lignocellulosic biomass is
fractionated to remove at least a portion of C5 saccharides by any
suitable means, including, but not limited to, hydrothermal treatment
(such as hot compressed water, subcritical, near critical, or
supercritical water, which may contain other fluids, including alcohol,
acid, or base), enzymatic treatment, and the like.

[0193] The methods of the invention are preferably run continuously,
although they may be run as batch or semi-batch processes.

[0194] The methods of the invention may be carried out in any suitable
reactor, including, but not limited to, a tubular reactor, a digester
(vertical, horizontal, or inclined), or the like. Suitable digesters
include the digester system described in U.S. Pat. No. B-8,057,639, which
include a digester and a steam explosion unit, the entire disclosure of
which is incorporated by reference.

[0195] In certain embodiments, the second supercritical or near-critical
fluid is substantially free of C1-C5 alcohols.

[0197] In certain embodiments, the step of fractionating comprises
contacting said lignocellulosic biomass with a first reaction fluid
comprising hot compressed water and, optionally, carbon dioxide; wherein
said first reaction fluid further comprises acid, when said
lignocellulosic biomass comprises softwood; and wherein said first
reaction fluid is at a temperature of at least about 100° C. under
a pressure sufficient to maintain said first reaction fluid in liquid
form. In certain embodiments, the acid is added as an aqueous acid, is
generated by contacting the first reaction fluid with a gaseous compound
that forms acid in situ; and/or is generated by contacting the first
reaction fluid with a solid acid catalyst. In certain embodiments, the
acid is an inorganic acid or an organic acid, or an acid formed in situ.
Inorganic acid include, but are not limited to: sulfuric acid, sulfonic
acid, phosphoric acid, phosphonic acid, nitric acid, nitrous acid,
hydrochloric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid.
Organic acids include, but are not limited to, aliphatic carboxylic acids
(such as acetic acid and formic acid), aromatic carboxylic acids (such as
benzoic acid and salicylic acid), dicarboxylic acids (such as oxalic
acid, phthalic acid, sebacic acid, and adipic acid), aliphatic fatty
acids (such as oleic acid, palmitic acid, and stearic acid), aromatic
fatty acids (such as phenylstearic acid), and amino acids. In certain
embodiments, the acid is preferably sulfuric acid, hydrochloric acid,
phosphoric acid, nitric acid, or a combination thereof. Gaseous compounds
that form acid in situ include, but are not limited to, SO2,
CO2, NO2, HX (where X is Cl, Br, F, or I), or a combination
thereof. Suitable solid acids include, but are not limited to, zeolites,
anionic exchange resins, and combinations thereof.

[0198] In certain embodiments, the step of contacting said adjusted pH
slurry with said second reaction fluid has a duration greater than about
2 seconds to about 5 seconds. In other embodiments, the step of
contacting said adjusted pH slurry with said second reaction fluid has a
duration of about 5 seconds to about 10 seconds.

[0199] In certain embodiments, the adjusted pH slurry has a pH of about pH
5.0 to about pH 8.0. In certain preferred embodiments, the adjusted pH
slurry has a pH of about pH 5.0 to about pH 6.0.

[0200] In certain embodiments, the step of increasing said pH of said
slurry comprises adding a base; wherein said base is selected from the
group consisting of an organic base, an inorganic base, and combinations
thereof. In certain preferred embodiments, the inorganic base is a
compound selected from the group consisting of sodium hydroxide, ammonium
hydroxide, calcium carbonate, and combinations thereof. In certain
particularly preferred embodiments, the inorganic base is sodium
hydroxide.

[0201] In certain embodiments, the C6 oligosaccharides and
monosaccharides may be fermented to ethanol, butanol, and mixtures
thereof, using techniques known to those skilled in the art, including,
but not limited to, yeast fermentations using Saccharomyces cerevisiae
and Clostridium sp. In certain preferred embodiments, an oligomer
fermentor is able to uptake oligomers directly (generally up to a maximum
size, for example, of 6 mer units, for Clostridium thermocellum).

[0202] In certain embodiments, the yield of said C6 monosaccharides
is at least 60% of theoretical yield, preferably, at least 65% of
theoretical yield.

[0203] In certain embodiments, the yield of said glucose is at least 60%
of theoretical yield, at least 63% of theoretical yield.

[0204] In certain embodiments, the invention is directed to the products
produced by the methods of the invention.

[0205] In further embodiments, the invention is directed to compositions
formed from lignocellulosic biomass, comprising:

[0206] C6 saccharides;

[0207] less than about 15%, preferably, less than about 10%, by weight,
based on the total weight of the composition, of byproducts, wherein said
byproducts are selected from the group consisting of glycolaldehyde,
glycolic acid, glyceraldehyde, and mixtures thereof; and

[0208] water;

[0209] wherein said C6 saccharides are produced from said
lignocellulosic biomass using supercritical or near critical fluids.

In certain embodiments, the C6 saccharide is glucose, galactose,
mannose, fructose, or a mixture thereof. In certain preferred
embodiments, the C6 saccharide is glucose. The compositions of the
invention are particularly useful as starting materials that may be
fermented into ethanol, butanol, and other useful materials.

[0210] Glycolaldehyde may be easily hydrogenated to mono-ethylene glycol
(MEG), using Raney nickel catalyst, for example. In addition, glycolic
acid, glycerolaldehyde, lactic acid, and acetic acid are generated, which
may be isolated using, for example, liquid-liquid extraction.

[0211] The products produced by the methods of the invention may be
utilized in a wide variety of applications, where C6 sugars are
conventionally utilized, including, but not limited to, the production of
various chemicals and fuels using fermentative, enzymatic, catalytic, and
non-catalytic (e.g., thermal decomposition) processes. Such processes are
useful for preparing feedstocks for the preparation of the following
non-exhaustive list:

[0217] The present invention is further defined in the following Examples,
in which all parts and percentages are by weight, unless otherwise
stated. It should be understood that these examples, while indicating
preferred embodiments of the invention, are given by way of illustration
only and are not to be construed as limiting in any manner. From the
above discussion and these examples, one skilled in the art can ascertain
the essential characteristics of this invention, and without departing
from the spirit and scope thereof, can make various changes and
modifications of the invention to adapt it to various usages and
conditions.

EXAMPLES

Example 1

Cellulose Hydrolysis

[0218] Lignocellulosic biomass was processed via a pre-treatment stage
wherein hot compressed water was added to a slurry of the lignocellulosic
biomass. Operating conditions were defined as:

[0221] The solids were then mixed with water to form a slurry. This feed
generally had a pH of about 4.2. It was then ramped up to a temperature
of 250° C. and this temperature was maintained for a small
residence time (defined as Pre-heating Stage). Slurry from this stage was
then impinged with supercritical water (1:1 weight ratio with respect to
the slurry) so that the slurry temperature was immediately raised to
reaction temperature. After maintaining this temperature for a certain
residence time (defined as Stage 1 of Cellulose Hydrolysis), the feed was
quenched with cool water to reduce temperature by about 30° C.
before sending it to the heat exchanger (defined as Quench Stage). This
is done to retard the reaction. Operating conditions were defined as
follows:

It is seen that the residence time of the reaction is extremely small and
this makes it very difficult to scale up.

Example 2

Modified Cellulose Hydrolysis

[0225] A solid containing 44.5% glucan and 7.3% xylan, was collected from
a pretreatment run at 240±10° C. and 1.7±0.5 minutes. Tap
water was used to make a 4% slurry and had an initial pH of 4-4.2. For
each run, the preheat condition was kept same as 250±5° C. for
20 seconds, the hydrolysis stage was conducted using different
temperature and residence time. Slurry pH was increased to different
values by adding certain amount of sodium hydroxide (NaOH) solution.
After solid/liquor separation, solid and liquor samples were analyzed
according to the National Renewable Energy Laboratory (NREL) standard
procedures. Table 2 lists the detailed experimental conditions.

[0226] The results are explained as functions of product yields, cellulose
conversion at different pH, temperature and residence time as shown in
FIG. 1 at a temperature of 335° C. FIG. 2 is a plot of % glucose
yield as a function of pH at different residence time of 335° C.
FIG. 3 is a plot of % cellulose conversion as a function of temperature
at different pH for a 5 s residence time for one embodiment of the
invention. FIG. 4 is a plot of % cellulose conversion as a function of
temperature at different pH for a 7 s residence time for one embodiment
of the invention. FIG. 5 is a plot of % glucose yield as a function of
temperature at different pH for a 7 s residence time for one embodiment
of the invention.

[0227] By increasing pH from 4.2 to about 5-6, the cellulose conversion
rate and sugar degradation rates were significantly decreased. For
example, the experiments show that at 340° C. at 7-10 s, 20%
oligomer yield and >50% glucose still remains in the solid.

[0238] Cellulose dissolution/hydrolysis can be catalyzed by acids. Hence
reducing the acidity is believed to be able to slow down the reactions.
From the above results, for the experiments with increasing pH (decreased
acidity): [0239] A. Glucose oligomer yields are decreasing [0240] B.
Cellulose conversions (as defined above) are also decreasing and less
cellulose were converted to water-soluble products.

[0241] While the preferred forms of the invention have been disclosed, it
will be apparent to those skilled in the art that various changes and
modifications may be made that will achieve some of the advantages of the
invention without departing from the spirit and scope of the invention.
Therefore, the scope of the invention is to be determined solely by the
claims to be appended.

[0242] When ranges are used herein for physical properties, such as
molecular weight, or chemical properties, such as chemical formulae, all
combinations, and subcombinations of ranges specific embodiments therein
are intended to be included.

[0243] The disclosures of each patent, patent application, and publication
cited or described in this document are hereby incorporated herein by
reference, in their entirety.

[0244] Those skilled in the art will appreciate that numerous changes and
modifications can be made to the preferred embodiments of the invention
and that such changes and modifications can be made without departing
from the spirit of the invention. It is, therefore, intended that the
appended claims cover all such equivalent variations as fall within the
true spirit and scope of the invention.